Networked systems using multiple processors are widely used, as for example by aircraft and other vehicles for fly- or control-by-wire applications, for command and control systems, and for warehouse inventory maintenance. In many such systems, various sources are used for providing information about the system's environment. In the context of an aircraft or vehicle, the sensors may measure speed, pitch, roll, yaw, fuel or propellant status, and the like, an provide such information, and various derivatives of the information, to the operator, and to motive and control devices. In the context of a command and control system, the sensors may include radar, sonar, and visual detection systems, and may also include own-vehicle sensors such as those mentioned for vehicle control, as well as additional sensors, such as for example GPS location sensors and weapon loading status sensors. In the context of a warehouse inventory control system, the sensors may include bar-code or other scanners, bin or other storage location full/empty status, and the like. In all cases, some of the data may be entered by hand, or may otherwise be essentially fixed over the short term, and other data may be provided as a stream of current data, representing a continual status update.
In such systems, processing may be performed at a variety of network nodes, and some of the nodes may be associated with local processing. In the context of a vehicle, a sensor, such as an actuator position sensor, may provide information to a local processor, which causes the actuator to assume the commanded state given the system status and environmental conditions, and which may take action in the event of malfunction. In the context of a command and control system, a vehicle or fixed site may have plural sensors for providing indications of status, position, speed and heading, altitude, weapon status, and fuel reserve, and the local processing may be on a vehicle-wide basis rather than on a subsystem basis, for control of the vehicle and its weapons. In the context of a warehouse, the system may automatically dispatch stored products from their known locations, monitor and reorder stock as required, receive replacement stock and route the replacements to suitable storage space, and the like.
In many such systems, the reliability or accuracy of the various computations will be enhanced by including in the calculations information from sensors at locations remote from the location at which the computations are being performed. In the context of a vehicle, plural fuel or propellant sensors may together provide information leading to a more accurate representation of the actual amount of fuel or propellant than a single sensor would provide. In the context of a command and control military system, determination of threats and potential targets may be enhanced by including in the computations information from radar systems other than the local radar system. In the context of a warehouse or storage system, the use of plural sensors associated with a product flow path may give information about product losses along the length of the path. Ideally, such systems would use all the available information in performing their calculations.
Networked systems are in common use. Their limitations are all too well known. For one thing, the transmission paths through a network take time, so that information cannot proceed instantly from one remote location to another. In addition, all transmission paths are subject to bandwidth or data rate limitations. For example, peaks in usage or utilization of a network can result in reduction in bandwidth available to all users, and can additionally result in lost data and or slow operation. In some contexts, slow operation may not be more than an inconvenience, but it may have economic impact in the warehouse situation, and life-threatening or otherwise disastrous impact in the case of a command and control system or a vehicle actuator controller. For this reason, it is desirable to control the data throughput of a networked system.
The “Link 16” system is a networked command and control system which is currently in use by the U.S. Navy. FIG. 1 is a simplified block diagram of a Link 16 system 10. In system 10 of FIG. 1, a first node 11 includes a command and control (C2) processing arrangement 14, which communicates with a network 18 by way of a Link 16 terminal 16. Another or second node 12 of system 10 also includes a C2 processing arrangement 22, which communicates with network 18 by way of a Link 16 terminal 20. Other similar nodes (not illustrated) are coupled to network 18 by way of paths designated as 19. In the arrangement of system 10 of FIG. 1, each of nodes 11 and 12 may be viewed as representing a vehicle. Many different types of messages are transmitted, in a broadcast manner, among the various nodes of the system 10. Among the message types which are communicated, there are engagement coordination messages, which are used to coordinate threat track numbers, to assure that multiple nodes do not simultaneously engage the same threat. Own-platform position messages are transmitted by each ship, vehicle or node, to identify to other nodes its own location, speed, and heading. Track association messages are transmitted under in the situation in which two previously separate tracks are determined to represent the same object. Track or target information is also transmitted between or among the various nodes of the Link 16 system. The track information includes track position information, track velocity information (which inherently includes track heading information), and track quality information (which inherently includes positional uncertainty information). The track information which is transmitted between or among the nodes of a Link 16 system also identifies the target as friend or foe, and includes identification of the source of the information and the time at which the information was generated. Link 16 controls network loading by prioritizing access to the network based upon the type of message which is to be transmitted. Thus, the priorities assigned to the various messages depend upon the preassigned categories.
Improved data transfer methods are desired for networked systems including plural nodes.